This invention relates to apparatus for producing an aroma in the surrounding atmosphere, and more particularly for doing so using an electrical heating element in proximity to a medium containing an aromatic liquid which element serves to create air currants that flow through the medium thereby assisting the evaporation of the aromatic liquid.
Many prior art devices exist wherein an electric light bulb in proximity to a liquid contained within a housing acts as the heating element to assist vaporization or evaporation of the liquid. See Gudeman U.S. Pat. No. 1,403,548; Rosenthal U.S. Pat. No. 1,706,939; Huff U.S. Pat. No. 2,591,818; Diehl U.S. Pat. No. 2,949,090; Weber III U.S. Pat. No. 3,080,624; and Spector U.S. Pat. No. 4,346,059. Other vaporizors are shown in Lockey U.S. Pat. No. 658,793 and Messina U.S. Pat. No. 2,515,310. Patents disclosing pressurized or mechanical dispensers of a liquid include Dearling U.S. Pat. No. 3,330,481; Valbona et al U.S. Pat. No. 3,864,080; Harrison U.S. Pat. No. 3,972,473; Dearling U.S. Pat. No. 4,084,732; and Hammond Br. Patent Spec. No. 1,443,314. Other documents of interest are the odor expelling toy in Locks et al U.S. Pat. No. 2,618,892; a lure for wild game which was a combustible fuel to generate heat in Bilyew U.S. Pat. No. 3,119,650; and German Pat. No. 2807383.
More recently aroma generating units which use an electrical heating element (other than a lamp) and disposable cartridge of some sort impregnated with the aromatic liquid to be dispersed have become popular. One such unit utilizes a flat circular cartridge adapted to be inserted horizontally into a slot within a housing. The unit contains a heating element below the slot.
The housing in the above described unit, except for the relatively narrow slot, completely encloses the heating element and associated electrical circuitry. Hence, there is little danger that in replacing cartridges one will come in contact with electrical parts or terminals. However, as designs change it becomes desirable to provide improved heating elements which will meet appropriate electrical safety requirements for use in more open housings where the heating element is more exposed during replacement of cartridges. At the same time heating element designs which provide automatic switching between more than one heat control setting and more uniform distribution of heat over the nearby disc are also desirable.